[unreadable] In modern Multislice CT scanners, the speed of image reconstruction lags far behind the rate of data collection. The objective of this work is to develop a fundamentally new, algorithmically-accelerated, fast and flexible hardware image backprojector. The algorithms to be employed were developed and patented by the University of Illinois. Using this technology, speed-up factors of 10-50 have been achieved in software demos. Multislice CT scanners will require the additional speed afforded by a special-purpose hardware implementation of the fast algorithms. Accordingly, the Phase I aims of this project are to 1) Design, implement, and optimize the mapping of a fast algorithm onto a field programmable gate array (FPGA) testbed to produce an ultra-fast reconfigurable hardware conebeam backprojector for circular source trajectories, and to 2) Benchmark the cost/performance of the prototype system with both an FPGA implementation of the conventional backprojection algorithm and with the performance of reconstruction engines used in current medical scanners. In Phase II, the FPGA prototype design will be extended to the important helical cone-beam geometry and will be ported to a custom processing board optimized for the architecture and for interface to the standard bus employed by CT manufacturers. The fast image reconstruction engine will greatly increase the throughput of CT scanners, reducing radiologist and patient waiting times, and speeding up diagnosis for critical trauma imaging. Fast reconstruction also will enable fullresolution dynamic real-time CT (e.g. for cardiac), reduced-dose imaging, and the use of computationally demanding exact algorithms for improved image quality. [unreadable] [unreadable]